burn in - Computer Definition

(1) To test a new electronic system by running it for some length of time. Although electronics can give out at any time, weak components often fail within the first few hours of use. For example, when a computer is built to order, it is often turned on and allowed to run for several hours before being released to the customer. See burn.

(2) (burn-in) The persistence of a faint image on CRTs and plasma TVs, both of which create a display by causing phosphors to glow. Also called "ghosting," burn-in occurs when static images are displayed continuously, and the glass is actually etched with the color phosphors. Quite common on early computer CRTs, it also occurred on first-generation plasma TVs. Although new plasma sets have burn-in countermeasures, the screen can still be burned if used for the same video game played hours on end with on-screen objects that never change.
Burn-In Vs. Image Retention
Although the terms "burn-in" and "image retention" are often used synonymously, burn-in is permanent, while image retention is temporary, and the image will disappear after some period of time. See CRT, plasma and LCD vs. plasma.